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This article presents a $W$ -band rectenna unit that incorporates a novel CMOS switching rectifier and a print tapered slot antenna. The operation principle of the switching rectifier is analyzed. The proposed rectifier topology shows improved reliability, and it utilizes the body-diode effect (BDE) to improve power conversion efficiency (PCE). Besides, a high-gain $W$ -band antipodal linearly tapered slot antenna is implemented on PCB to improve the overall efficiency. In order to demonstrate the utility of the proposed rectenna unit for large-scale rectenna array, a $1\times 2$ (parallel) and $2\times 2$ (series-parallel) rectenna arrays in 40-nm bulk CMOS technology and PCB process have been implemented. The switching rectifier achieves a peak PCE of 45.8% at 94GHz with improved reliability. Occupying only 0.0756 mm2, the overall PCEs of the rectenna unit and the $2\times 2$ rectenna array are 25% and 23%, delivering 5.6- and 20-mW output dc power, respectively, at 90-mW/cm2 incident power density. The proposed rectifier and rectenna array achieve the highest PCE among recently reported $W$ -band rectifiers and rectenna arrays with different technologies. [ABSTRACT FROM AUTHOR]

We study the entanglement dynamics of two static atoms coupled with a bath of fluctuating scalar fields in vacuum in the cosmic string spacetime. Three different alignments of atoms, i.e. parallel, vertical, and symmetric alignments with respect to the cosmic string are considered. We focus on how entanglement degradation and generation are influenced by the cosmic string, and find that they are crucially dependent on the atom-string distance r, the interatomic separation L, and the parameter ν that characterizes the nontrivial topology of the cosmic string. For two atoms initially in a maximally entangled state, the destroyed entanglement can be revived when the atoms are aligned vertically to the string, which cannot happen in the Minkowski spacetime. When the symmetrically aligned two-atom system is initially in the antisymmetric state, the lifetime of entanglement can be significantly enhanced as ν increases. For two atoms which are initially in the excited state, when the interatomic separation is large compared to the transition wavelength, entanglement generation cannot happen in the Minkowski spacetime, while it can be achieved in the cosmic string spacetime when the position of the two atoms is appropriate with respect to the cosmic string and ν is large enough. [ABSTRACT FROM AUTHOR]

This article proposes the concept of millimeter-wave (mm-wave) switching rectifiers originated from drain-pumped mixers. The topology and circuit design methodology are distinctly different from other CMOS mm-wave rectifiers which adopt voltage multiplier techniques. Operation principle and RF-to-dc power conversion efficiency (PCE) of the proposed switching rectifiers are analyzed to overcome the fundamental limits on achievable performance of switching rectifiers at mm wave. In order to demonstrate the utility of the proposed concept, two prototypes in 65-nm bulk CMOS technology have been implemented: two fully integrated switching rectifiers operating at Ka-band and W-band. A peak PCE of 36.5% at 35 GHz with a load resistance of $50~\Omega $ at about 15-dBm input power is measured for the Ka-band rectifier. Measurement results for the W-band rectifier also indicate that the PCE peaks at 27% at 91 GHz for a load resistance of $43~\Omega $ at about 16-dBm input power. To the best of our knowledge, the two fully integrated rectifiers which occupy the smallest chip area exhibit a competitive PCE reported among Ka-band and W-band CMOS rectifiers, competing well with GaAs counterparts where the Schottky diode is available. [ABSTRACT FROM AUTHOR]